1. Field of the Invention
The present invention relates to a concrete form member for assembling a concrete form employed for placing concrete or forming a concrete secondary product in construction work or engineering works, for example.
2. Description of the Prior Art
In general, a wooden form member prepared by nailing cross bars to a plywood board or a metal form member prepared by fixing metal ribs to an iron plate or an aluminum plate is known as this type of concrete form member. As a typical example of the conventional wooden form member, FIG. 11A shows a form member 70 prepared by fixing a flat plate 71 of plywood, for example, to a plurality of reinforcing cross bars 72 with nails 73. In order to assemble a concrete form with such form members 70, nails 73 are driven into adjacent reinforcing cross bars 72 of the form members 70 for connecting and fixing the same to each other. FIG. 11B shows an exemplary concrete form having a cross-shaped concrete forming part 74 assembled in the aforementioned manner. The flat plate 71 may be formed by a plastic plate, in place of the plywood board.
An example of a conventional form member space holder for fixing a pair of form members 70 at a prescribed space through concrete placing surfaces when assembling a concrete form with the form members 70 is described with reference to FIGS. 12 and 13A to 13C. Referring to FIG. 12, the conventional form member space holder is mainly formed by a separator 121, attachments 122 and clamp members 123. The separator 121 is formed by a bar provided with a pair of male screws 121a on both ends thereof, as shown in FIG. 13A. Each male screw 121a is fitted with a female screw 122c provided on an end of each attachment 122 shown in FIG. 13B. The attachment 122 is provided on another end with a male screw 122d, which is substantially coaxial with the female screw 122c, passing through a separator mounting hole 76 provided in each form member 70 so that an end of a substantially truncated-conical presser 122a of resin engaging with the outer periphery of an attachment body part 122b is in contact with the concrete placing surface of the form member 70. A female screw 123a provided on an end of each clamp member 123 is fitted with the male screw 122d of the attachment 122, thereby clamping/fixing the attachment 122 to the form member 70.
A male screw 123b is provided on another end of the clamp member 123, so that a support member 124 and a nut 125, mounted on this male screw 123b fix thin cylindrical form support members 126 of a metal to bridge a plurality of transversely arranged form members 70.
As a typical example of the conventional metal form member, FIG. 14A shows a form member 80 prepared by bonding/fixing side plates 82 and reinforcing plates 83 to a metal flat plate 81. FIG. 14B shows an exemplary concrete form having a cross-shaped concrete forming part 84 assembled by a plurality of such metal form members 80. In this form, metal auxiliary members 85 are employed on corners of the cross-shaped concrete forming part 84, in addition to the form members 80.
Japanese Utility Model Laying-Open No. 62-54149 (1987) discloses a conventional form member of synthetic resin. In the form member of synthetic resin described in this literature, reinforcing projections are integrally provided on four points on the rear surface of a plate member of plastic having a square front surface. These projections have receiving holes for connectors, while receiving holes for separators are formed in prescribed portions of the plate member.
Among the aforementioned conventional form members, the wooden form member is lightweight and has a degree of freedom in execution. However, the wooden form member has such disadvantages that the same can be reused only three or four times since the plywood board absorbing strong alkaline moisture starts to come off from an end portion when used several times, requires skill for assembling/execution, is unsuitable for global environmental protection due to consumption of Laura as raw material and industrial wastes resulting after use, and is not applicable to high-grade concrete having a low slump and high strength due to limitation of employment of a vibrator resulting from low strength.
Further, the hygroscopius plywood board absorbs moisture from a surface of placed concrete, which is in contact with the plywood board, and an ideal water-cement ratio of the concrete is lost in this portion, to result in rough finishing of the outer surface of the concrete. In this case, the concrete may be erroneously regarded as defectively hardened. Therefore, prescribed coating is applied to the surface of the plywood board for reducing its hygroscopius. However, the cost for such a coated plywood board is unpreferably increased.
Although the metal form member has high strength, the degree of freedom in working is so small that the executable range is limited and the form member is hardly applicable to general construction work. Further, the heavy metal form member must inevitably be reduced in size, leading to inferior execution efficiency. Further, the metal form member is generally rusted or unusably deformed if insufficiently managed, and extremely hard to repair in such a state.
In order to solve the aforementioned problems of the conventional concrete form members, the inventor has already proposed the structure of a concrete form member shown in FIGS. 15 to 17 in U.S. Pat. No. 5,632,923.
As shown in FIGS. 15 and 16, an improved concrete form member 1 proposed in the aforementioned literature has a main plate portion 3 formed by such a long flat plate that the length between both longitudinal ends 3B (showing in FIG. 17, is set about 10 times that between both cross-directional ends 3A, with flat front and rear surfaces 3C and 3D. A pair of side plate portions 4 are formed by long strip-shaped bodies perpendicularly extending from the cross-sectional ends 3A of the main plate portion 3 toward the rear surface 3D to face each other, and surfaces 4A thereof are flatly formed. Further, a pair of rear plate portions 5 are formed by long strip-shaped bodies perpendicularly extending inward from both cross-directional forward ends 4B of the side plate portions 4 to face the rear surface 3D of the main plate portion 3. Surfaces 5A of the rear plate portions 5 are flatly formed while forward ends thereof inwardly project to form reinforcing thick portions 5B.
A plurality of mounting holes 6 are formed along the cross-directional center of the main plate portion 3 of the form member at prescribed intervals in the longitudinal direction. Further, a plurality of mounting holes 7 are formed in each of the pair of side plate portions 4 in correspondence to the positions of the mounting holes 6 of the main plate portion 3. Each mounting hole 7 is arranged on a position at a prescribed distance L from the front surface 3C of the main plate portion 3 along the cross direction. In addition, a plurality of mounting holes 8 are formed in each of the pair of rear plate portions 5 in correspondence to the positions of the mounting holes 6 of the main plate portion 3. Each mounting hole 8 is formed on a position at a distance L, identical to the distance L between the center of each mounting hole 7 and the front surface 3C of the main plate portion 3, from the surface 4A of each side plate portion 4 along the cross direction.
As shown in FIGS. 17 and 18, each of end plate bodies 9 engaging with both longitudinal ends of a form member body 2 is formed by a flat horizontal end plate portion 10 shielding each longitudinal end of the form member body 2 and a pair of vertical end plate portions 11 and 12 perpendicularly extending from front and rear ends of the horizontal end plate portion 10, and has a substantially U-shaped section. The horizontal end plate portion 10 is formed to engage with a space, having a rectangular plane shape, enclosed with the main plate portion 3, the pair of side plate portions 4 and the pair of rear plate portions 5. In the pair of vertical end plate portions 11 and 12, the front end surface of the front vertical end plate portion 11 is in contact with and fixed to the rear surface 3D of the main plate portion 3, while the rear vertical end plate portion 12 is formed to face the vertical end plate portion 11 and engage with the pair of rear plate portions 5. All surfaces 10A, 11A and 12A of the horizontal end plate portion 10 and the pair of vertical end plate portions 11 and 12 are flatly formed.
The horizontal end plate portion 10 is provided on its longitudinal center with a mounting hole 13, which is arranged on a portion at a distance, substantially identical to the distance L, between the center of each mounting hole 7 and the surface 3C of the main plate portion 3, from the surface 3C of the main plate portion 3 along the cross direction of the horizontal end plate portion 10, as shown in FIG. 18. Further, a mounting hole 14 is formed on the longitudinal center of the rear vertical end plate portion 12, and the center of this mounting hole 14 is arranged on a portion at a distance, substantially identical to the distance L, from the surface 10A of the horizontal end plate portion 10 along the cross direction of the vertical end plate portion 12.
In such an improved conventional concrete form member, each of the form member bodies 2 and the end plate bodies 9 can be prepared by integral forming of fiber-reinforced plastic to implement a relatively lightweight form member having high strength while improving workability in assembling, thereby solving the aforementioned problems of the prior art.
In the structure of the aforementioned improved conventional concrete form member, however, the main plate portion 3 of the form member body 2 is readily concavely deflected and. deformed to open the pair of side plate portions 4 due to pressure applied by concrete in concrete placing. When assembling a form, therefore, a reinforcing member must be brought into contact with the form member for clamping the same in order to ensure flatness of a surface of the formed concrete.